Hydraulic torque converters, devices used to change the ratio of torque to speed between the input and output shafts of the converter, have revolutionized energy transfer from engines. This is especially apparent in vehicles such as automobiles, trucks, tractors, and boats where hydraulic means is provided to transfer energy from a power shaft of an engine to a drive mechanism, e.g., drive shaft or automatic transmission, while smoothing out engine power pulses. A torque converter, arranged between the engine and a transmission, includes three primary components: an impeller, sometimes referred to as a pump, directly connected to the converter's cover and from the converter's cover to the engine's power shaft, e.g. a crankshaft; a turbine, similar in structure to the impeller, however the turbine is connected to the input shaft of the transmission; and, a stator, located between the impeller and turbine, which redirects the flow of hydraulic fluid exiting from the turbine thereby providing additional rotational force to the pump.
A cross sectional view of a common torque converter configuration is shown in FIG. 2.
The three main components of the torque converter as shown in FIG. 2 are the pump 37, turbine 38, and stator 39. The stator is used to redirect the flow of returning fluid to increase efficiency. The turbine and the pump are rotatable assemblies, in large part formed in the shape of hollow shells 22, 24, respectively that rotate radially. The torque converter 10 becomes a sealed chamber when the pump 37 is welded to a cover 11. In common embodiments, the cover 11 is connected to flexplate 41 which, in turn, may be bolted to a crankshaft 42 of an engine 7 (FIGS. 1 and 2). The cover can be connected to the flexplate using lugs or studs welded to the cover. The welded connection between the pump and cover transmits engine torque to the pump. Therefore, the pump always rotates at engine speed. The function of the pump is to use this rotational motion to propel fluid radially outward and axially toward the turbine. Therefore, the pump is a centrifugal pump propelling fluid from a small radial inlet to a large radial outlet, increasing the energy in the fluid.
In a torque converter 10 a fluid circuit is created by the pump (sometimes called an impeller), the turbine, and the stator (sometimes called a reactor). The fluid circuit allows the engine to continue rotating when the vehicle is stopped, and to accelerate the vehicle when desired by a driver. The torque converter supplements engine torque through torque ratio, similar to a gear reduction.
Turbine 38 uses the fluid energy it receives from pump 37 to propel the vehicle. Turbine shell 22 is connected to a turbine hub 19. Turbine hub 19 usually uses a spline connection to transmit turbine torque to transmission input shaft 43. The input shaft is connected to the wheels of the vehicle through gears and shafts in transmission 8 and axle differential 9 (FIG. 1). The force of the fluid impacting the turbine blades is output from the turbine as torque.
FIG. 2 does not clearly show means for attachment of blades to a turbine or pump. This figure may be considered non-pertinent prior art.
Torque converters as above described are well known in the art. Traditionally, the blades have been connected to their respective pump or turbine by means of welding. It is to be understood that “welding” in this sense is to be broadly construed. “Welding” is intended to include the following:
Direct fusion of the blades to the shell of the pump or turbine by melting and subsequent hardening at their interface;
Connection by means of an intermediate or connecting molten metal as occurs in gas or arc welding using a metal connecting material usually selected from copper, iron and alloys of at least two of iron, copper, tin, zinc, lead, aluminum, silver, cobalt, chromium and nickel, an example of this method being described in U.S. Pat. No. 3,673,659; and
Connection using a plastic material that is usually a cross linked organic plastic such as an epoxy resin, e.g. as described in U.S. Pat. No. 3,817,656.
The most common form of welding utilized has been brazing.
It has been suggested that blades might be secured without welding by utilizing mechanical fastenings such as tabs on a blade that are inserted through a slit, slot or recess in a pump or turbine shell. Unfortunately, such devices have had serious disadvantages.
A major disadvantage has been that the blade is not held as securely as when welding is used and the blade may thus vibrate to cause noise, part wear and eventual catastrophic failure. Examples of such devices are described in U.S. Pat. Nos. 2,660,957; 3,673,659; 5,794,436 and 5,893,704.
A further major disadvantage has been that there has been an inability, by such mechanical fastening, to obtain a tight fit of the blade with the pump or turbine shell. This results in significant inefficiency since fluid at the pump can pass between the blade and pump shell thus failing to direct that portion of the fluid to the turbine with the attendant loss of efficiency. This loss of efficiency is further increased by fluid passing between blades and the turbine shell thus failing to direct kinetic energy in that fluid to turn the turbine. Examples of such devices are described in U.S. Pat. Nos. 2,660,957; 3,673,659 and 5,794,436.
Yet another disadvantage is that the mechanical method of attachment may be difficult, complex or time consuming, e.g. rivets or similar connectors are required or the blades and bodies are of complex shapes that are difficult or expensive to manufacture and may require complex interlocking. Examples of such devices are for example disclosed in U.S. Pat. Nos. 2,660,957; 3,673,659; and 5,794,436.
U.S. Pat. No. 5,893,704 describes a structure; wherein, tabs on the blades are described that fit within recesses in the shell of a turbine. An advantage resulting from this structure is that fluid flow between the blades and the shell is restricted thus increasing efficiency. Unfortunately, the increased efficiency is not as great as desired because fluid flow around the blade is only stopped at the location of the tab and fluid can still flow around the blade at other locations because the tab, as a practical matter, cannot be expected to hold the rest of the edge of the blade tightly against the shell. This is true at least due to variations in insertable distance of the tab and variations in curvature of the shell relative to curvature of the blade. A further serious disadvantage of this structure is that there is no positive holding force applied to the blade since the tab does not pass through the shell of the turbine but merely rests within a depression by friction.
All of the U.S. patents described above are incorporated by reference herein as background art.